A study was conducted to assess the effects of a multi-component community-based project intervention on changing knowledge of, and attitudes towards early marriage for girls in The Gambia. The study involved a cross-sectional household survey of 201 male and female parents and 296 adolescent boys and girls aged 10-19. It also included two community-based focus group discussions and six key informant interviews. The study compared the project baseline and midline data in the analysis of the survey data. The findings show a significant increase from a baseline of (44.8%) to (70.7%) at midline among the parents who have the view that the girl needs to come of age (18 years) before going into marriage. At both baseline and midline, there is a fear that girls may break their virginity by indulging in premarital sex if they do not marry early. However, there was a significant decrease from (51.7%) at baseline to (10%) (p-value <0.001) in the proportion of parents who think girls must marry early to avoid premarital sex. The findings show between (2%) and (7%) increase from baseline to midline on the view among adolescent boys and girls that girls have the right to choose who to marry. Findings from the focus group discussions and key informant interviews directly linked the changes in knowledge of attitudes towards early marriage among parents and adolescents to the project intervention.